Water pollution is a worldwide problem. Almost anything released into the air or onto the land can end up in Earth’s water.

Surface Water Pollution

Water pollution may come from one source. For example, chemicals from a factory may empty into a stream. Water pollution may come from more than one source. For example, chemicals may rain from the air into that same stream. It is much more difficult to control pollution from more than one source.

In the developed nations there are three main sources of water pollution:

Chemicals that are applied to farm fields include fertilizers and pesticides (see Figurebelow). Excess chemicals can be picked up by rainwater. The chemicals can end up in streams, ponds, lakes or the ocean. Dissolved fertilizer causes tremendous numbers of water plants and algae to grow. This can lead to dead zones where nothing can live in lakes or the coastal oceans.

Waste from livestock can also pollute water. The waste contains pathogens that can cause diseases. Many farms in the U.S. have thousands of animals. These farms produce millions of gallons of waste. The waste is stored in huge lagoons, like the one in Figurebelow. Many leaks from these lagoons have occurred.

This is a pond of hog manure. Check out the vehicles at the bottom of the picture for scale.

Municipal

“Municipal” refers to the community. Households and businesses in a community can pollute the water supply. Municipal pollution comes from sewage, storm drains, septic tanks, boats, and runoff from yards. For example:

People apply chemicals to their lawns. The excess can run off into surface waters.

People may dispose of harmful substances incorrectly. For example, motor oil must not be drained into a storm sewer.

Municipal sewage treatment plants dump treated wastewater into rivers or lakes. But the wastewater may not be treated enough or for everything.